My truck has a BD exhaust brake that was put in by the previous owner. I had my wife give it some gas in drive with the E brake on and didn't see the linkage move at all. Is there another way to see if it still works right?!

 

yea drive it down the road and turn it on and see if it works

 

the dealer didn't explain anything, i don't think they knew anything either. Where would the switch usually be?!

 

If it was wired properly, it won't activate while you're pressing on the throttle. There should be a switch(could be mounted just about anywhere)to enable it, then another switch on the throttle linkage under the dash that will activate it when you let off the fuel.
Or, just to add to the confusion, on the 98.5-up trucks, it could be wired directly into the ECU, with just the above mentioned enable switch.